Method and apparatus of cross-connecting optical fibers with layered substrates forming fiber optic ribbons

ABSTRACT

A method is provided for cross-connecting individual optical fibers of a plurality of fiber optic ribbons and includes the steps of providing first and second substrates having adhesive thereon. Individual optical fibers are routed on the substrates to form at least portions of fiber optic input ribbons and fiber optic output ribbons, with the fibers extending beyond the substrates to define input and output tails. One substrate is positioned on top of another substrate, and a ribbonizing apparatus is used to gather the input and output tails in ribbon form whereupon they can be coated to hold the tails in their ribbon form.

This application is a Divisional of 10/045,876, filed on Nov. 07, 2001,now U.S. Pat. No. 6,597,845.

FIELD OF THE INVENTION

This invention generally relates to the art of optical fibers and,particularly, to a method of cross-connecting or reorganizing theindividual optical fibers of a plurality of fiber optic ribbons and anapparatus for facilitating ribbonizing the individual fibers.

BACKGROUND OF THE INVENTION

Fiber optic circuitry is increasingly being used in electronics systemswhere circuit density is ever-increasing and is difficult to providewith known electrically wired circuitry. An optical fiber circuit isformed by a plurality of optical fibers carried by a dielectric, and theends of the fibers are interconnected to various forms of connectors orother optical transmission devices. A fiber optic circuit may range froma simple cable which includes a plurality of optical fibers surroundedby an outer cladding or tubular dielectric to a more sophisticatedoptical backplane or flat fiber optic circuit formed by a plurality ofoptical fibers mounted on a substrate in a given pattern or circuitgeometry.

One type of optical fiber circuit is produced in a ribbonizedconfiguration wherein a row of optical fibers are disposed in aside-by-side parallel array and coated with a matrix to hold the fibersin the ribbonized configuration. In the United States, a twelve-fiberribbon or an eight-fiber ribbon have become common. In other foreigncountries, the standard may range from as a low as four to as high astwenty-four fibers per ribbon. Multi-fiber ribbons and connectors have awide range of applications in fiber optic communication systems. Forinstance, optical splitters, optical switches, routers, combiners andother systems have input fiber optic ribbons and output fiber opticribbons.

With various applications such as those described above, the individualoptical fibers of input fiber optic ribbons and output fiber opticribbons are cross-connected or reorganized whereby the individualoptical fibers of a single input ribbon may be separated and reorganizedinto multiple or different output ribbons. The individual optical fibersare cross-connected or reorganized in what has been called a “mixingzone” between the input and output ribbons.

Optical backplanes are fabricated in a variety of manners, ranging fromlaying the optical fibers on a substrate by hand to routing the opticalfibers in a given pattern or circuit geometry onto the substrate bymechanized apparatus. The individual optical fibers are cross-connectedor reorganized on the substrate between input and output ribbonsprojecting from input and output ends or edges of the substrate.Therefore, the above-mentioned “mixing zone” is provided by thesubstrate, itself.

When cross-connecting optical fibers on substrates of opticalbackplanes, problems often are encountered because of the spacelimitations of a given application. In other words, the size of thesubstrate may be limited, but it may be necessary in a givenspecification to have more individual optical fibers in the input andoutput ribbons than the limited sized substrate can handle. This isparticularly true when fabricating the optical backplane by mechanizedapparatus. For example, a routing apparatus with a routing head mayrequire 4-5 mm both in front of and behind a first laid optical fiberfor laying a second fiber over the top of the first fiber. This requiresan amount of space or “real estate” on the substrate. Obviously, if asubstrate has a limited size, only a limited number of individualoptical fibers can be cross-connected or reorganized on the substrate,and this limited number of individual fibers may be insufficient tofabricate input and output ribbons to meet a particular specification.Consequently, it may be necessary to fabricate a layered backplanewherein one or more substrates (with their limited number of routedfibers) are stacked on top of another substrate (with its limited numberof routed fibers), whereby the fibers of the stacked substrates arecombined to form the specified input and output ribbons.

Heretofore, multi-layered backplanes or circuits have been fabricated byplacing a bottom layer adhesive coated substrate on a base sheet ofadhesive coated paper-like material on top of a flat table or otherplatform. Individual optical fibers are placed on the bottom layersubstrate and base sheet, with the fibers projecting beyond edges of thesubstrate to form ribbon tails. A conformal coating is applied to thebottom layer substrate and fibers, and the coating is cured. A second ortop layer substrate is placed on top of the bottom layer, and individualoptical fibers again are placed on the top layer substrate with endportions of the fibers extending outwardly onto the base sheet to formribbon tails. A conformal coating is applied to the top layer substrateand all of the ribbon tails, and the coating is cured. The layeredsubstrate and ribbon tails then are peeled off of the base sheet, andthe base sheet is discarded. Such methods or processes can only be madeby hand and, typically, one operator follows the entire process fromstart to finish for consistency reasons. A double-layered backplane maytake as long as a full 8-hour day to complete. In addition, hand routingor laying of the fibers is difficult for maintaining straight lines anduniform ribbon tails with the tiny individual optical fibers.

The present invention is directed to solving these various problems in amethod of manufacturing a multi-layer backplane or optic circuit whichis particularly applicable for mechanized fabrication and involves theuse of a simple ribbonizing apparatus.

SUMMARY OF THE INVENTION

An object, therefore, of the invention is to provide a new and improvedmethod of cross-connecting the individual optical fibers of a pluralityof fiber optic ribbons to form a backplane or other flat opticalcircuit.

Another object of the invention is to provide a new ribbonizingapparatus for gathering a plurality of individual optical fibers intoribbon form.

In the exemplary embodiment of the invention, the method includes thesteps of providing a first substrate having an adhesive thereon. Aplurality of individual optical fibers are routed onto the substrate toform at least portions of a plurality of fiber optic input ribbons,reorganizing the fibers on the substrate and forming at least portionsof a plurality of fiber optic output ribbons, with the fibers extendingbeyond input and output sides of the substrate to define input tails andoutput tails of the input ribbons and output ribbons, respectively. Asecond substrate is provided with an adhesive thereon. A plurality ofindividual optical fibers are routed onto the second substrate to format least portions of a plurality of fiber optic input ribbons,reorganizing the fibers on the second substrate and forming at leastportions of a plurality of fiber optic output ribbons, with the fibersextending beyond input and output sides of the second substrate todefine input tails and output tails of the input ribbons and outputribbons, respectively.

The second substrate and the fibers routed thereon then is placed on topof the first substrate and the fibers routed thereon, such that thefibers of the two substrates combine to form complete input and outputribbons along with their respective input and output tails. Aribbonizing apparatus is used to gather the input and output tails intoribbon form. The gathered input and output tails are coated on theribbonizing apparatus to hold the tails in ribbon form. The coated tailsthen are stripped from the ribbonizing apparatus. In the preferredembodiment, the individual optical fibers are routed onto the substratesby a mechanical routing apparatus having a routing head. Preferably, acoating is applied over the fibers routed on the first and secondsubstrates.

The ribbonizing apparatus includes a frame and a plurality of elongatedribbonizing plates. Each plate is configured for receiving a pluralityof individual optical fibers and gathering the fibers into ribbon form.Means are provided for mounting at least some of the ribbonizing plateson the frame for lateral movement relative thereto to adjust therelative positions of the plates.

According to one aspect of the invention, each ribbonizing plateincludes a shallow trough in a top face thereof. At least one end of thetrough is open for laying the fibers thereinto. The frame includes aplurality of longitudinal frame components joined by a plurality ofcross frame components on which the ribbonizing plates slidably rest.According to another aspect of the invention, the mounting meansincludes at least one guide rod extending transversely through theribbonizing plates and along which the ribbonizing plates are slidablymovable. The frame includes a pair of longitudinal side frame componentsbetween which the rod extends. The frame also includes at least a crossframe component on which the ribbonizing plates slidably rest.

Other objects, features and advantages of the invention will be apparentfrom the following detailed description taken in connection with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of this invention which are believed to be novel are setforth with particularity in the appended claims. The invention, togetherwith its objects and the advantages thereof, may be best understood byreference to the following description taken in conjunction with theaccompanying drawings, in which like reference numerals identify likeelements in the figures and in which:

FIG. 1 is a top plan view showing the fabrication of the bottom layercircuit of the multi-layer backplane of the invention;

FIG. 2 is a top plan view of the top layer circuit of the multi-layerbackplane;

FIG. 3 is a top plan view showing the top layer circuit positioned ontop of the bottom layer circuit;

FIG. 4 is a view similar to that of FIG. 3, showing a ribbonizingapparatus for use in gathering and ribbonizing the fiber optic tails;

FIG. 5 is a top plan view of the final configuration of the multi-layerbackplane or optical circuit;

FIG. 6 is a top plan view of another embodiment of a universalribbonizing apparatus;

FIG. 7 is a top plan view of the setup plate of the apparatus of FIG. 6;

FIG. 8 is an edge elevational view of the setup plate of FIG. 7;

FIG. 9 is a top plan view of one of the side frame components of theapparatus of FIG. 6;

FIG. 10 is a top plan view of one of the cross frame components of theapparatus of FIG. 6;

FIG. 11 is an edge elevational view of the cross frame component of FIG.10;

FIG. 12 is a plan view of one of the guide rods of the apparatus of FIG.6;

FIG. 13 is a side elevational view of one of the elongated ribbonizingplates of the apparatus of FIG. 6;

FIG. 14 is an enlarged vertical section taken generally along line 14—14of FIG. 13;

FIG. 15 is an enlarged vertical section taken generally along line 15—15of FIG. 6;

FIG. 16 is an enlarged vertical section taken generally along line 16—16of FIG. 6;

FIG. 17 is an enlarged section taken generally along line 17—17 of FIG.6; and

FIG. 18 is an elevational view of a mechanical routing apparatus havinga routing head.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings in greater detail, FIGS. 1-5 show somewhatschematically the steps in the method or process of the invention forfabricating a multi-layer backplane or optical circuit, and FIGS. 6-17show the structure of a universal ribbonizing apparatus for use with themethod of the invention. The method of fabricating a multi layerbackplane or optical circuit, generally designated 20 (FIG. 5), firstwill be described.

In particular, FIG. 1 shows the first steps in fabricating the backplaneand involves the fabrication of a bottom layer circuit, generallydesignated 22. A first substrate 24 is provided with an adhesive coatingon the top thereof. The substrate has an input side 24 a and an outputside 24 b. A plurality of input fingers 24 c project from input side 24a, and a plurality of output fingers 24 d project from output side 24 b.Bottom layer substrate 24 may be supported on a flat platform or othertable-like support structure.

A plurality of individual optical fibers 26 then are routed, preferablyby a mechanized apparatus, onto bottom layer substrate 24 to form atleast portions of a plurality of fiber optic input ribbons, generallydesignated 28, with the fibers being reorganized on the substrate toform at least portions of a plurality of fiber optic output ribbons,generally designated 30. Although the reorganization can varyconsiderably, the circuit pattern illustrated herein involves fourindividual optical fibers from each input ribbon 28 being routed to oneof a pair of output ribbons 30 to complete the composite of the outputribbons, whereby each output ribbon includes eight individual fibers. Itcan be seen that the fibers extend beyond input and output fingers 24 cand 24 d, respectively, at input and output sides 24 a and 24 b,respectively, of bottom layer substrate 24 to form input tails 32 andoutput tails 34 of loose optical fibers. A conformal coating of plasticmaterial then is applied over bottom layer substrate 24 and theindividual fibers 26 routed thereon. The individual fibers in inputtails 32 and output tails 34 remain loose.

A top layer circuit, generally designated 36, then is fabricated as seenin FIG. 2. The top layer circuit is similar to bottom layer circuit 22in that it includes a top layer substrate 38 having an adhesive coatingthereon. The top layer substrate includes an input side 38 a and anoutput side 38 b, but there are no input and output fingers such asinput and output fingers 24 c and 24 d, respectively, of the bottomlayer substrate shown in FIG. 1.

A plurality of individual optical fibers 40 then are routed, preferablyby a mechanized apparatus, onto top layer substrate 38 to form at leastportions of a plurality of input ribbons, generally designated 42, and aplurality of output ribbons, generally designated 44. The individualfibers extend beyond input side 38 a and output side 38 b of the toplayer substrate to form input tails 46 and output tails 48 of looseindividual fibers. A conformal coating of plastic material then isapplied over top layer substrate 38 including the individual opticalfibers 40 thereon, leaving the fibers in input tails 46 and output tails48 loose.

Again without in any way limiting the considerable number of circuitpatterns that can be routed on top layer substrate 38, two individualoptical fibers 40 from each input ribbon 42 are routed to one of theoutput ribbons 44, so that each output ribbon is complete with eightindividual fibers.

Referring to FIG. 3, top layer circuit 36 then is placed on top ofbottom layer circuit 22, with top layer substrate 38 overlying bottomlayer substrate 24. The bottom layer substrate cannot be seen in FIG. 3except for input fingers 24 c and output fingers 24 d of the bottomlayer substrate.

When the top layer circuit is superimposed over the bottom layercircuit, it can be seen that input tails 32 of the bottom layer circuitlay alongside input tails 46 of the top layer circuit. With theindividual fibers 26 of the bottom layer circuit being shown in phantomin FIG. 3, it can be seen that partial input ribbons 28 of the bottomlayer circuit combine with partial input ribbons 42 of the top layercircuit to form complete input ribbons comprised of eight individualfibers corresponding to the eight fibers of each of the output ribbons30 and 44. The end result is that there are four input ribbons of eightfibers and four output ribbons of eight fibers, with the individualfibers of the ribbons being cross-connected and reorganized on thesubstrates of the bottom and top layer circuits as shown by the full andphantom lines in FIG. 3. Finally, it can be seen that the individualfibers of partial input tails 32 and 46 and complete output tails 34 and48 still remain loose in FIG. 3. FIG. 4 shows a ribbonizing apparatus,generally designated 50, which includes a frame, generally designated52, formed by a pair of side frame components 54 joined by a pluralityof cross frame components 56. A plurality of elongated ribbonizingplates 58 are adjustably mounted on a pair of guide rods 60 which extendthrough the ribbonizing plates. Each ribbonizing plate has a shallowtrough 62 in the top surface of the plate.

FIG. 4 also shows the individual loose fibers of output tails 48 and 34having been gathered and positioned into shallow troughs 62 ofribbonizing plates 58 so that the individual fibers are in aside-by-side flat or ribbon array. A conformal plastic coating then isapplied over the ribbons after they are gathered in troughs 62. Thecoating is allowed to cure, whereupon the individual fibers of theribbons are held in ribbon form. At least troughs 62 of ribbonizingplates 58 are coated with a release material, such as Teflon or thelike, and the ribbonized output tails are easily stripped out of thetroughs and away from ribbonizing apparatus 50.

Ribbonizing apparatus 50, or a second apparatus similar thereto, then isused to ribbonize the loose fibers of the input tails shown at theleft-hand side of FIG. 4. The resulting product is a multi-layerbackplane or optical circuit as shown at 20 in FIG. 5. In other words,top layer circuit 36 (FIG. 2) has been juxtaposed on top of bottom layercircuit 22 (FIG. 1) as described above in relation to FIG. 3. The loosefibers of the input and output tails then are ribbonized as describedabove in relation to FIG. 4, resulting in the final configuration of amulti-layer backplane or optical circuit 20 shown in FIG. 5.

FIG. 6 shows an alternate embodiment of a ribbonizing apparatus,generally designated 50A, which is similar to ribbonizing apparatus 52shown in FIG. 4 and described above. Therefore, like numerals areapplied in FIGS. 6-17 corresponding to like components described aboveand shown in FIG. 4.

More particularly, ribbonizing apparatus 50A (FIG. 6) includes a frame,generally designated 52, which includes a pair of side frame components54 joined by a plurality of cross frame components 56 along with a frontsetup plate or platform 64. A plurality of elongated ribbonizing plates58 are slidably or adjustably mounted on a plurality of guide rods 60which extend between side frame components 54.

Setup plate 64 of ribbonizing apparatus 50A is shown in FIGS. 7 and 8.The setup plate includes opposite stepped sides 64 a having throughholes 64 b.

One of the side frame components 54 is shown in FIG. 9. Each side framecomponent includes a plurality of vertical through holes 54 a and aplurality of horizontal through holes 54 b, along with a set of verticalholes 54 c.

One of the cross frame components 56 is shown in FIGS. 10 and 11. Eachcross frame component includes opposite stepped ends 56 a having throughholes 56 b. One of the guide rods 60 is shown in FIG. 12. Each guide rodsimply is an elongated solid shaft-like member having a roundconfiguration in cross-section.

One of the elongated ribbonizing plates 58 is shown in FIGS. 13 and 14.Each ribbonizing plate has three enlarged, horizontal through passages58 a for slidably mounting the ribbonizing plates on the three guiderods 60 shown in FIG. 6. A shallow, flat trough 62 is formed in a topsurface 58 b of each ribbonizing plate for gathering the individualfibers in ribbon form as described above in relation to FIG. 4. At leastthe trough is coated with Teflon material so that the ribbonized fiberscan be easily stripped therefrom, again as described in relation to FIG.4.

In assembly of universal ribbonizing apparatus 50A (FIG. 6), ribbonizingplates 58 are “threaded” onto guide rods 60, with the guide rodsextending through passages 58 a (FIG. 14) as seen in FIGS. 6 and 17.With the ribbonizing plates positioned onto the guide rods, the guiderods are inserted into through holes 54 b (FIG. 9) in side framecomponents 54. Set screws 69 (FIG. 17) which are threaded through sideframe components 54 then are used to hold or fix the guide rods to theside frame components, while ribbonizing plates 58 are free to move backand forth on the guide rods in the direction of double-headed arrow “A”(FIG. 6). The ends of side frame components 54 (FIG. 9) then arepositioned into stepped opposite sides 64 a of setup plate or platform64 (FIG. 7) and are bolted thereto by fasteners positioned through holes64 b in the setup plate and holes 54 c in the side frame components. Theopposite stepped ends 56 a of cross frame components 56 (FIGS. 10 and11) then are secured to the undersides of side frame components 54 asseen in FIG. 16, with fastening bolts inserted through holes 56 b in thecross frame components aligned with holes 54 b in the side framecomponents. Ribbonizing plates 58 then can be adjusted to preciselyalign troughs 62 of the ribbonizing plates with the fibers of theinput/output tails of the multi-layer backplane circuit.

The difference between universal ribbonizing apparatus 50A (FIG. 6) andribbonizing apparatus 50 shown in FIG. 4, is that the universalapparatus has many (20) more ribbonizing plates 58 for use with a widevariety of backplane or optical circuit configurations having aconsiderable number of input and/or output tails. Ribbonizing apparatus50 shown in FIG. 4 is a custom apparatus for the specific backplane orcircuit used herein to exemplify the invention. Nevertheless,ribbonizing plates 58 of apparatus 50 (FIG. 4) can slide along guiderods 60 to precisely align troughs 62 with the loose fiber endsprojecting from the substrates of the top and bottom layer circuits. Ineither embodiment, the juxtaposed top and bottom circuits are positionedas shown in FIG. 4, with substrate output fingers 24 d (or input fingers24 c) resting on top of setup plate or platform 64 and abutting the endsof ribbonizing plates 58. The components are dimensioned so that theindividual fibers of the input and output tails can be laid continuouslyfrom fingers 24 d or 24 c directly into troughs 62 of the ribbonizingplates, as the ribbonizing plates rest on top of cross frame components56 and a front lip 64 c of setup plate 64 as seen in FIGS. 15 and 16.

Individual optical fibers 26 are routed onto bottom layer substrate 24,and individual fibers 40 are routed onto top layer substrate 38 by amechanical routing apparatus, generally designated 70 in FIG. 18, whichincludes a routing head 72. The apparatus including the routing head canpivot about an axis 74 as it moves in the direction of arrow 76. Anindividual optical fiber 77 is fed into a funnel 78 of the apparatus andis fed to a needle 80 which applies the fiber to substrates 24 and 38,whereby the fibers are held onto the substrates by the adhesive materialon the substrates. The apparatus includes a cut-off mechanism as isknown in the art. Further details of such a routing apparatus can bederived from co-pending application Ser. No. 09/645,624, filed Aug. 24,2000, assigned the assignee of the present invention, and which isincorporated herein by reference.

It will be understood that the invention may be embodied in otherspecific forms without departing from the spirit or centralcharacteristics thereof. The present examples and embodiments,therefore, are to be considered in all respects as illustrative and notrestrictive, and the invention is not to be limited to the details givenherein.

What is claimed is:
 1. A method of cross-connecting the individualoptical fibers of a plurality of fiber optic ribbons, comprising thesteps of: providing a first substrate having an adhesive thereon;routing a plurality of individual optical fibers onto the substrate toform at least portions of a plurality of fiber optic input ribbons,reorganizing the fibers on the substrate and forming at least portionsof a plurality of fiber optic output ribbons, the fibers extendingbeyond input and output sides of the substrate to define input tails andoutput tails of the input ribbons and output ribbons, respectively;providing a second substrate having an adhesive thereon; routing aplurality of individual optical fibers onto the second substrate to format least portions of a plurality of fiber optic input ribbons,reorganizing the fibers on the second substrate and forming at leastportions of a plurality of fiber optic output ribbons, the fibersextending beyond input and output sides of the substrate to define inputtails and output tails of the input ribbons and output ribbons,respectively; placing the second substrate and the fibers routed thereonon top of the first substrate and the fibers routed thereon, such thatthe fibers of the two substrates combine to form complete input andoutput ribbons along with their respective input and output tails; usinga ribbonizing apparatus to gather the input and output tails into ribbonform; coating the gathered input and output tails on the ribbonizingapparatus to hold the tails in ribbon form; and stripping the coatedtails from the ribbonizing apparatus.
 2. The method of claim 1 whereinsaid individual optical fibers are routed onto the substrates by amechanical routing apparatus having a routing head.
 3. The method ofclaim 1, including the step of applying a coating over the fibers routedonto the first substrate.
 4. The method of claim 1, including the stepof applying a coating over the fibers routed onto the second substrate.5. A method of cross-connecting the individual optical fibers of aplurality of fiber optic ribbons, comprising the steps of: providing afirst substrate having an adhesive thereon; routing a plurality ofindividual optical fibers onto the substrate by a mechanical routingapparatus having a routing head to form at least portions of a pluralityof first fiber optic ribbons, reorganizing the fibers on the substrateand forming at least portions of a plurality of second fiber opticribbons, the fibers extending beyond the substrate to define first tailsand second tails of the first ribbons and second ribbons, respectively;applying a coating over the fibers routed onto the first substrate;providing a second substrate having an adhesive thereon; routing aplurality of individual optical fibers onto the second substrate by amechanical routing apparatus having a routing head to form at leastportions of a plurality of first fiber optic ribbons, reorganizing thefibers on the second substrate and forming at least portions of aplurality of second fiber optic ribbons, the fibers extending beyond thesecond substrate to define first tails and second tails of the firstribbons and second ribbons, respectively; applying a coating over thefibers routed onto the second substrate; and placing the secondsubstrate and fibers routed thereon on top of the first substrate andthe fibers routed thereon, such that fibers of the two substratescombine form complete first and second ribbons along with theirrespective first and second tails.
 6. The method of claim 5, includingthe step of using a ribbonizing apparatus to gather the first and secondtails into ribbon form.
 7. The method of claim 6, including the step ofcoating the gathered first and second tails on the ribbonizing apparatusto hold the tails in ribbon form.
 8. The method of claim 7, includingthe step of stripping the coated tails from the ribbonizing apparatus.